In the late 11th century when Beatus' text began to be used less frequently, the Silos monks decided to undertake the expensive task of producing a copy of this work: expensive because the codex required extremely fine parchment, a variety of inks, and gold. In order to produce a well-finished and well-presented work, skilled calligraphers and illuminators were also necessary. The monks Domingo and Munio set to work and on Thursday, April 18th 1091, they finished the task of copying the text, which may have taken them several months. Subsequently, at an unknown moment, it was enlarged by the addition of several lavishly decorated folios taken from an antiphonary, also from Silos, and a vision of hell, a unique specimen in Romanesque art.

The Silos Beatus is undoubtedly one of the most beautiful of all those that have survived. This book features every single miniature from the codex together with their description.